Separation Processes in the Food and Biotechnology Industries - Prins and Applns

296 Pages·1996·17.513 MB·English

by  A. Grandison, M. Lewis

SEPARATION PROCESSES
IN THE FOOD AND
BIOTECHNOLOGY
INDUSTRIES
Principles and Applications
Edited by
A. S. GRANDISON and M. J. LEWIS
Department of Food Science and Technology
University of Reading, UK
WOODHEADP UBLISHING LIMITED
Cambridge England
Published by Woodhead Publishing Limited, Abington Hall,
Abington, Cambridge CB 1 6AH, England
First published 1996
0 1996, Woodhead Publishing Ltd
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British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
ISBN I 85573 287 4
Typeset by Heather FitzGibbon, Christchurch, Dorset
Printed by Galliard (Printers) Ltd, Great Yarmouth, England
Preface
This book concentrates on the more recent methods and techniques for separating food
components and products of the biotechnology industry. Each chapter deals with a
specific type or area of application and includes information on the basic principles,
industrial equipment available, commercial applications and an overview of current
research and development.
The introductory chapter gives a brief overview of food composition and properties,
and some of the heat and mass transfer considerations in batch and continuous processes.
Separations from solids, liquids and gases are briefly discussed. A summary is provided
of the more conventional separation techniques such as screening, filtration and
centrifugation, and techniques for removing water, such as evaporation, freeze-
concentration and dehydration. However, the main emphasis is on separation processes,
which have received less attention in textbooks on food-engineering and food-processing
operations. It is hoped that this book will complement and supplement many of these
excellent texts. Chapter 2 deals with the use of supercritical fluids for extraction
processes, with special reference to carbon dioxide. Chapter 3 deals with pressure-
activated membrane techniques, and covers the general principles, reviews the
applications of reverse osmosis, and serves as an introduction to Chapters 4 and 5, which
deal specifically with the principles and applications of ultrafiltration and microfiltration
respectively. The separation and recovery of charged particles by ion exchange and
electrodialysis is covered in Chapter 6. Chapter 7 discusses innovative separation
processes, and reviews some of the methods being actively investigated, some of which
are now coming into industrial practice. Much of the emphasis in these chapters is on the
separation and recovery of proteins and biologically active ingredients. Chapter 8 is
specifically on the methods available for fractionating fat, and covers the upsurge in
interest and recent developments in this area. The book concludes with a chapter on
solids separation processes, with special reference to particulates. The physical properties
which influence the separation are reviewed, together with sieving, screening and air
classification. Wet processing methods for extraction are discussed, together with some
miscellaneous applications such as dehulling, peeling and cleaning.
xii Preface
Much of the emphasis is on extraction of macromolecules, increasing the added value
of foods and recovering valuable components from by-products and fermentation media.
Many of the methods discussed are now in commercial practice, whilst others are being
vigorously researched.
A. S. Grandison and M. J. Lewis
Contents
...........................................................
Preface xi
- ..................................
1 Separation processes an overview 1
A . S . Grandison and M . J . Lewis
1.1 Foods - the raw material ... ............................... 1
1.2 Separation techniques ... ............................... 5
1.2.1 Introduction ...... ............................... 5
1.2.2 Separations from solids ....................................... 7
Solid-solid separations ................................. 8
Separation from the solid matrix ............................ 9
1.2.3 Separations from liquids ..................................... 10
Liquid-solid separations ................................... 10
Immiscible liquids ........................................ 11
General liquid separation processes ........................... 11
1.2.4 Separations from gases and vapours ............................ 13
1.3 Water treatment ................................................. 15
1.4 References ..................................................... 15
....
2 Supercritical fluid extraction and its application in the food industry 17
D . Steytler
2.1 Introduction ................. ............................... 17
2.2 The supercritical fluid state ..... ............................... 18
2.2.1 Physical properties of NCF CO, ............................... 20
Density ................................................ 20
Viscosity ............................................... 21
Diffusion ............................................... 22
Volatility (vapour pressure) ................................. 23
Chemical properties ...................................... 23
Biochemical properties ............................... 24
vi Contents
2.3 Properties of NCF solutions ....................................... 24
2.3.1 Solubilities in NCFs ........................................ 24
General principles ........................................ 25
Effect of molecular structure .............................. 25
Effect of temperature and pressure ......................... 28
2.3.2 Theoretical models (equations of state (EOS)) ..................... 28
Entrainers ............................................... 34
2.3.3 Diffusion coefficients ........................................ 35
2.4 Factors determining the efficiency of NCF extraction ................... 36
2.4.1 Extraction stage ............................................ 37
Mechanism of extraction ................................... 37
The ‘free diffusion’ model ................................ 38
The ‘shrinking core’ model ............................... 38
Solubility ............. ............................... 40
Diffusion coefficient ...................................... 40
Adsorption .............................................. 40
The role of water ......................................... 41
2.4.2 Separation stage ............................................ 42
2.5 Equipment and experimental techniques used in NCF extraction and
fractionation ................................................... 44
2.5.1 Extraction ............... ........................
Pilot plants with recirculati ............................... 44
Small pilot plant with total loss of COZ ...
2.5.2 Fractionation .............................................. 46
Cascades of separation vessels ....................
Zosel’s ‘hot finger’ fractionation column ...................
2.6 Applications ..............................................
2.6.1 Decaffeination of coffee and tea ............................... 49
2.6.2 Seed oil extraction .......................................... 51
2.6.3 Purification of lecithin ....................................... 52
2.6.4 Lowering cholesterol levels in foods ............................ 53
2.6.5 Fractionation of high-value oils and fats ......................... 53
Butterfat ................................................ 53
Fish oils ................. ............................ 54
2.6.6 Extraction of flavours and fragrances ........................... 54
2.7 References ..................................................... 57
............................
3 Pressure-activated membrane processes 65
M . J . Lewis
3.1 Introduction .................................................... 65
3.2 Terminology .................................................... 66
3.3 Concentration factor and rejection .................................. 69
3.4 Membrane characteristics ......................................... 70
3.5 Permeate rate ................................................... 71
3.6 Transport phenomena and concentration polarisation ................... 72
Contents vii
3.7 Membrane equipment ............................................ 75
3.7.1 Membrane configuration ..................................... 76
3.8 Safety and hygiene considerations .................................. 82
3.9 Reverse osmosis applications .................................... 86
3.9.1 Introduction ............................................... 86
3.9.2 Water treatment ............................................ 87
3.9.3 Milk processing ............................................ 88
3.9.4 Fruit and vegetable juices .................................... 90
3.9.5 Other applications ..... ........................... 91
3.10 References ................ .....................
..................................................
4 Ultrafiltration 97
M . J . Lewis
4.1 Introduction .................................................... 97
4.2 Processing characteristics ......................................... 98
4.2.1 Rejection or retention factors ................................. 98
4.2.2 Yield ................ ................................. 101
4.2.3 Average rejection ...... ................................. 103
4.2.4 Practical rejection data ...................................... 104
4.3 Performance of ultrafiltration systems ............................... 105
Permeateflux ............................................ 105
4.3.1 Transport phenomena and concentration polarisation .......... . 106
4.3.2 Fouling ................ ........................... 111
4.3.3 Factors affecting flux ... ............................... 114
Energy input ....... ........................... 114
4.4 Diafiltration .................................................... 116
Introduction ............................................. 116
4.4.1 Washing out at constant volume ............................... 116
Washing-in ............................................. 118
4.4.2 Diafiltration applications ... ............................ 119
4.4.3 Protein fractionation .............................
4.5 Ultrafiltration applications ... ... ...............
4.5.1 Dairy applications . . ...........................
4.5.2 Oilseed and vegetable proteins ............................ 125
4.5.3 Animal products ........................................... 127
4.5.4 Biotechnology applications ................................... 128
Membrane-based bioreactors ............................... 128
Enzyme reactors ......................................... 128
Membrane fermenters ..................................... 131
Recovery of components and downstream processing ............ 132
4.5.5 Medical applications: serum fractionation ......................... 133
4.6 References ..................................................... 134
viii Contents
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 Microfiltration , , , 141
A. S. Grandison and T. J. A. Finnigan
5.1 Introduction .................................................... 141
5.2 Theory, materials and equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
, , , ,
5.2.1 Membrane configurations and characteristics . . . . . . . . . . . . . . . . 142
, , , , ,
5.2.2 Performance of microfiltration systems and membrane fouling . . . . . . . 146
5.3 Applications in the food and biotechnology industries . . . . , . . . , . . . . . . . . . . 148
5.3.1 Food industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
I
5.3.2 Applications for biotechnology . .......................... 150
5.4 Conclusions ............... . . . . . . ........ ......... 151
5.5 References . . . . . . . . . . . ....................... 152
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 Ion-exchange and electrodialysis.. 155
A. S. Grandison
6.1 Ion-exchange . . . . . . . . . . . . . . . . . . . . ......................... 155
6.1.1 Theory, materials and equipment
Solute/ion-exchanger interactions . . . . . , , . . . . . . . . . . . . . . . . . . . . 155
Ion-exchange groups . . . . . . . . . . . . . , , , , . . . . . . . . . . . . . . . . . . . . . 158
Ion-exchange materials . . . . . . . . . . . . . . . . . . . . . . . . .
.......................
....................
Elution ................................................. 159
Ion-exchange columns ......................... 160
Mixed bed systems . . . ............................... 160
Stirredtanks ............................................ 160
6.1.2 Applications of ion-exchange in the food and biotechnology industries 160
Softening ............................................... 161
Demineralisation . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . 16 1
Decolorisation . . . . . ............................
Protein purification . . . ................................ 163
Purification of other compounds . . . . . . . . . . . , . . . . . . . . .
6.2 Electrodialysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........ 166
6.2.1 Theory and equipment . . . . . . . ...................... 167
6.2.2 Applications of ED in the food an
6.3 References . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . .
7 Innovative separation methods in bioprocessing 179
J. A. Asenjo and J. B. Chaudhuri
7.1 Introduction .................................................... 179
7.2 System characteristics . . . . . . . . . . . . , . . , . . . . . . . , . . . . . . , , . . . . . . . . . . . . 180
7.2.1 Physicochemical basis for separation operations . . . . . . . . . . . . . . . 180
, , , ,
7.2.2 Kinetics and mass transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1
, , ,
7.3 Liquid-liquid extraction: introduction , . , , , . . . . . . . . . . . , . . . . . . . . . . . . . . , 181
7.3.1 Aqueous two-phase separation . . . . . . . . . . . . . . . . . . . . . . . . 182
, , ,
7.3.2 Reverse micelle extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
,
Contents ix
7.3.3 Perfluorocarbon affinity separations ..............
...........
7.4.1 Adsorption system
7.4.2 Continuous adsorption recycle extraction. ........
7.4.3 Membrane chromatography .............................
7.4.4 Chromatographic and adsorption materials ........ 201
7.5 Other developments ......... ..........
7.5.1 Electrically enhanced separations ... .................. 202
.................
7.6 References ............ ............. 204
.................. ..........................
8 Fractionation of fat , 207
K. K. Rajah
8.1 Introduction .................... ................
.......... ........... 210
8.2 Dry fractionation ................ ................ 211
8.2.1 Flat-bed vac ....................
Vacuband batch filter. ....................
8.2.2 Rotary drum filters ................. .............. 215
8.2.3 Membrane filters ...... ...............
Low pressure ............. ...................
........ 224
....................
8.3 Detergent fractionation ................
................ 232
8.4 Solvent fractionation ...... .............
8.5 References .................... ................ 238
.......................................
9 Solids separation processes 243
M. J. Lewis
9.1 Introduction ..... ..............
9.2 Physical properties of solids. ............ ................ 244
9.2.1 Classification of powders .............
9.2.2 Particle size and particle size distribution ................... 247
9.2.3 Particle density .....................
9.2.4 Forces of adh ...................... 252
9.2.5 Bulk properties ...........
9.2.6 Bulk density and porosity .............
9.2.7 Flowability ..... .....................
x Contents
9.3 Separation of particulates and powders ............................... 256
9.3.1 Size reduction .............................................. 256
9.3.2 Sieving ................................................... 258
9.4 Air classification ................................................. 260
9.4.1 Introduction ................................................. 260
9.4.2 Commercial air classifiers .................................... 262
9.4.3 Process characterisation ...................................... 264
9.4.4 Applications ............................................... 268
9.4.5 Cereal separations .......................................... 268
9.4.6 Legumes .................................................. 270
9.4.7 Other applications .......................................... 273
9.5 Wet separation processes .......................................... 273
9.5.1 Protein recovery ..........
9.5.2 Soya processing .........................
9.5.3 Wheat protein ....................................
9.5.4 Other applications ................
9.6 Some miscellaneous solids separations .........................
9.6.1 Dehulling ...........................................
9.6.2 Peeling ................................................... 279
9.6.3 Cleaning of raw materials ..................................... 279
9.6.4 Sorting and grading ......................................... 281
Colour sorting and grading ................................. 281
9.7 References ..................................................... 283
..............................................................
Index 287